Firstly install GTA IV PC, now to install GTA IV PC without getting the error "Not Compatible with this Operating System %P" you need to open the DVD Contents here's how... by going to Computer > and at the E: folder
Now in there go down to setup.exe and then do the following right click on setup.exe then go to the Compatibility tab and set it to this:
Right click on the IV icon and do Open, in there click GTA IV and then go to the Redistributable folder, click these that are have a red circle round them.
Now click on these, this will install them.
If you are one of the few who are not having problems with installing the C++ app and GFWL, skip this part.
Now, once you have installed them through that way you will need to update GFWL without having this error while starting up IV!
You will need to go to this page to get IV up and running without the following error up top: http://www.rockstarg.../PC/GFWLupdate/
Download that and your ready to go, if you want to gain more FPS I recommend installing the Official V1 patch from Rockstar Games and also installing these drivers (181.20)
Edited by Indi., 13 January 2009 - 11:39 PM.